1. Field of the Invention
The present invention relates to a substrate transfer apparatus of a substrate processing system, and more particularly, to a substrate transfer apparatus used in an inline film deposition system which deposits a film on a diskshaped substrate such as a magnetic disk or optical disk having a center hole. Further, this present invention relates to a technique for shortening a loading/unloading time to improve the throughput in film deposition etc. when loading or unloading a substrate by the transfer operation in the substrate transfer apparatus.
2. Description of the Related Art
A substrate transfer apparatus related to the present invention is disclosed in Japanese Unexamined Patent Publication (Kokai) No. 8-274142. This publication discloses an in-line film deposition system. This film deposition system includes a plurality of vacuum chambers functioning as film deposition chambers and other processing chambers. The plurality of vacuum chambers is connected continuously in series in a ring. Due to this, a polygonal ring-shaped transport path is formed. In this transport path, a substrate rotation vacuum chamber including a rotational mechanism is provided at each of corners. FIG. 1 of this publication shows a substrate loader for loading an unprocessed substrate from the outside to an in-line film deposition system and a substrate unloader for unloading a processed substrate from the inside of the film deposition system to the outside. The substrate loader mounts the substrate loaded into the film deposition system onto a carrier and moves it, for example, in the clockwise direction along the polygonal ring-shaped transport path to receive the necessary processing in the individual vacuum chambers. After the processing is completed, the substrate is unloaded to the outside by the substrate unloader.
The substrate loader and the substrate unloader are respectively provided with substrate transfer mechanisms and each of them functions as a substrate transfer apparatus.
The "substrate transfer apparatus" means an apparatus which takes out two substrates from substrate cassettes carrying a plurality of (25 etc.) substrates and mounts the two substrates to the substrate holders provided on the carrier moving inside the chambers of the in-line film deposition system, for example. In taking out and mounting the substrates according to the substrate transfer apparatus, for example, operations for picking up the substrates from the substrate cassettes, moving them, and mounting them onto holders are performed. The substrate transfer apparatus is provided with a robot having an arm for performing these operations. Further, in the above case, the substrate to be transferred is disk shaped and has a center hole. In transferring the substrate, the center hole is used as a hook portion when picking up the substrate.
Next, a more detailed explanation will be given about a conventional substrate transfer apparatus with reference to the figures. In this explanation, FIG. 6 to FIG. 9 will be referred.
FIG. 6 is a plane view of a substrate loader and a substrate unloader in the above in-line film deposition system. This figure schematically shows the internal structures of the substrate loader and part of the transport path. The substrate loader 101 and substrate unloader 102 are connected to a vacuum chamber 100 forming the part of the transport path. FIG. 6 shows only the internal structure of the substrate loader 101. The substrate loading operation in the substrate loader 101 and the substrate unloading operation in the substrate unloader 102 are opposite to each other. In the following paragraph, the transfer operation of a conventional typical substrate transfer apparatus will be explained by describing the substrate loading operation of the substrate loader 101.
The vacuum chamber 100 serving as part of the transport path is connected to vacuum chambers 103 provided at its both sides and is connected through these vacuum chambers 103 to vacuum chambers 104 forming the polygonal ring-shaped transport path. Valve gates 105 are provided between the vacuum chamber 100 and the vacuum chambers 103. Processing for film deposition is performed in the plurality of vacuum chambers 103 forming parts of the transport path. Reference numeral 106 indicates a carrier moving along the transport for carrying or transporting the substrates. The carrier 106 moves in the direction of the arrows 107. The vacuum chambers 103 are positioned at corners or bent portions of the polygonal transport path. Rotational mechanisms are built inside the vacuum chambers 103. Due to the rotational mechanisms, the direction of movement of the carrier 106 moving along the transport path is changed. Examples of the specific structures of the rotational mechanisms of the vacuum chambers 103 and polygonal transport path are disclosed in the above Japanese Unexamined Patent Publication (Kokai) No. 8-274142 for example. A detailed explanation will be omitted here.
The substrate loader 101 connected to the vacuum chamber 100 is comprised of one vacuum chamber 108 and two auxiliary vacuum chambers 109 and 110. The vacuum chamber 108 is connected to the above vacuum chamber 100 and includes a built-in robot 111 for the substrate loading operation. The auxiliary vacuum chambers 109 and 110 are connected to the vacuum chamber 108 through gate valves 112 and 113. In FIG. 6, the gate valve 112 is in the open state, while the gate valve 113 is in the closed state. The auxiliary vacuum chambers 109 and 110 are provided with loading doors, that is, gate valves 114 and 115, connected to the outside. The unprocessed substrates are introduced into the auxiliary vacuum chambers 109 and 110 through the gate valves 114 and 115. The auxiliary vacuum chambers 109 and 110 are provided with substrate cassettes 117 each carrying, for example, 25 substrates 116 arranged in a single row in a standing state in parallel with center axes aligned. The substrate cassettes 117 are affixed inside the auxiliary vacuum chambers 109 and 110. Only the substrates are introduced into the auxiliary vacuum chambers 109 and 110. At the auxiliary vacuum chambers 109 and 110, first, the inside and outside pressures are adjusted, and the gate valves 114 and 115 are operated to open the chambers to the atmosphere. Afterward, 25 unprocessed substrates are introduced, the gate valves 114 and 115 are closed and the chambers is evacuated, and the gate valves 112 and 113 are opened to transfer the substrates by the robot 111. These operations are repeated. The auxiliary vacuum chambers 109 and 110 are alternately used. The robot 111 moves as shown by the arrows 120 to pick up two substrates 116 from the substrate cassette 117 by the substrate pickup portion 119 formed at the front end of the front arm 18. Then it rotates as shown by the arrows 121 and moves the front arm 118 as shown by the arrows 122 to mount the two substrates 116 at predetermined locations of the holders of the carrier 106.
In the above, the auxiliary vacuum chambers 109 and 110, the vacuum chamber 100 forming the part of the transport path, and the vacuum chamber 108 provided with the robot 111 are evacuated up to a required vacuum level at desirable timings. The evacuation system is provided below the vacuum chamber. Here, the illustration and explanation of the evacuation system will be omitted since it is well known.
FIG. 7 shows an example of the substrate cassette 117. The substrate cassette 117 is comprised of four rods 130 arranged substantially in parallel. The four rods 130 are connected by end frames so that both ends thereof satisfies the positional relationship shown in FIG. 7. In FIG. 7, for convenience of the explanation, the illustration of the end frames is omitted. The substrate cassette 117 configured by the four rods 130 is in a state that at least the front end thereof in FIG. 7 is opened. A total of 25 grooves (not shown) are formed at predetermined equal intervals (for example, d) in the axial direction at least at locations inside the circumferential surfaces of the four rods 130. These grooves support the substrates 116. Due to this, the 25 substrates 116 are supported by the four rods 130, that is, the substrate cassette 117. The four rods 130 are placed in a positional relationship with the substrates 116 so as to support the substrates at the bottom halves. Therefore, in the substrate cassette 117, 25 substrates 116 are arranged at equal intervals of d in parallel and in a single row. Note that the substrates 116 are disk-shaped substrates such as magnetic disks or optical disks having center holes 116a. In present invention, the center holes 116a are used as hook parts, so each of the substrates 116 is required to have the center hole 116a. The substrates 116 carried in a substrate cassette 117 in this way are picked up by the robot 111 two at a time. The front end of the front arm 118 of the robot 111 is formed with two grooves 131 at an interval d. The substrates 116 are picked up by these grooves 131. The grooves 131 form the above pickup portion 119.
The appearance of the robot 111 is shown in FIG. 8. The robot 111 is provided with a rotating shaft 142 on a base 141. A base arm 143 is affixed on the top end of the rotating shaft 142. The base arm 143 is structured to rotate freely around the rotating shaft 142. The outside end of the base arm 143 has an intermediate arm 144 attached to it in a freely rotating manner. Further, the front arm 118 is provided to freely rotate at the outside end of the intermediate arm 144. The front arm 118, strictly speaking, is formed with a large base portion (118a) having a high strength. The front portion is formed as a thin or narrow portion (118b) able to be inserted into the center hole 116a of the substrate 116. At the top surface of the front end of the front arm 118 is formed the above pickup portion 119 (two grooves 131). The pickup portion 119 of the front arm 118 is made to move freely as shown by the arrows 120 and 121 based on the operation of the robot 111.
The carrier 106 is shown in FIG. 9. The carrier 106 is comprised of two holders 151 for carrying substrates 116 and a slider 152 provided with these holders. The carrier 106 has a plate-like shape overall and is used in a longitudinally standing state. The two holders 151 are each formed with circular holes 151a. The substrates 116 are attached to the holes 151a in the standing state. The holes 151a are provided with finger-like spring members (not shown) for holding down the substrates, for example. Under the slider 152 are alternately arranged N-pole and S-pole magnets 153. As shown by the arrow 107 the slider 152 is moved by the rotation drive mechanism using magnetic coupling provided under the bottom plate of the vacuum chamber 100.
Next, an explanation about the operation for loading substrates by the conventional substrate loader 101 having the above configuration will be made by referring to FIG. 6 to FIG. 9.
FIG. 6 shows the state where the auxiliary vacuum chamber 109 is evacuated to a required vacuum pressure in the state that the 25 substrates 116 are set in the substrate cassette 117 of the auxiliary vacuum chamber 109, the gate valve 112 is opened, and two substrates 116 are picked up from the substrate cassette 117 in the auxiliary vacuum chamber 109 and successively mounted to the two holders 151 of carriers 106 moving in the vacuum chamber 100. The robot 111 simultaneously takes out two substrates 116 from the substrate cassette 117 by the pickup portion 119 formed at the front end of the front arm 118 utilizing the center holes 116a as the hook parts and mounts them one by one to the two holders 151 of the carrier 106. The pickup portion 119 of the robot 111 holds the two substrates 116 arranged in the front-back direction. In this way, the 25 substrates 116 in the substrate cassette 117 set in a auxiliary vacuum chamber 109 are mounted two by two in the holders of the carriers 106 successively moved to the vacuum chamber 100 by the robot 111 of the vacuum chamber 108. During this time, the other auxiliary vacuum chamber 110 is opened once to the atmosphere, and unprocessed substrates are introduced through the loading door, that is, the gate valve 115. After the transfer operation of the robot 111 with respect to the substrate cassette 117 of the auxiliary vacuum chamber 109 is completed, the gate valve 112 of the auxiliary vacuum chamber 109 is closed, the gate valve 113 of the auxiliary vacuum chamber 110 is opened, and the robot 111 continues transferring substrates in the same way as above for the 25 substrates 116 newly introduced in the substrate cassette 117.
The substrate unloader 102 is configured substantially the same except for performing an operation opposite to the substrate transfer operation at the substrate loader 101. Therefore, the same reference numerals are assigned to the vacuum chamber, two auxiliary vacuum chambers, gate valves, etc. in the substrate unloader 102.
In the transfer operation of substrates by the conventional substrate loader 101, two substrates 116 are placed one by one in the holders 151 of the carrier 106 by the robot 111, so the mounting operation has to be performed two times. If the robot 111 picking up the two substrates 116 from the substrate cassette 117 does not successively perform the operation for mounting a substrate on the carrier 106 two times, the operation for mounting substrates on the next carrier cannot be performed. Therefore, in an in-line film deposition system, the transport speed of the carriers carrying the processed objects, that is, the substrates, is restricted by the operating speed of the substrate transfer by the robot 111. As a result, there was the problem that the throughput of the film deposition system as a whole is reduced and the production capacity of the system as a whole is restricted. To solve this problem, in so far as the configuration for substrate transfer of the related art is utilized, it is necessary to further increase the operating speed of the robot 111. Further increasing the operating speed of the robot itself, however, is difficult as the limit has been reached at the present time.